1. Field of the Invention
The present invention relates to a fuel cell generally, and more particularly, to a fuel reforming apparatus of a fuel cell system.
2. Description of the Related Art
As is known, a fuel cell is constructed as a system for generating electrical energy using a fuel.
In the fuel cell, a polymer electrolyte membrane fuel cell has an excellent output characteristic, a low operating temperature, and fast starting and response characteristics. In addition, the polymer electrolyte fuel cell advantageously has a wide range of applications including a mobile power source for vehicles, a distributed power source for homes or buildings, and a small-sized power source for electronic apparatuses.
A fuel cell system incorporating the polymer electrolyte membrane fuel cell is typically constructed with a fuel cell body which is referred to as a stack (hereinafter, for convenience, referred to as “stack”), a fuel reforming apparatus which reforms the fuel to generate a reformed gas containing hydrogen and supplies the reformed gas to the fuel cell body, and an oxidant gas supply unit which supplies an oxidant gas to the stack.
Therefore, the polymer electrolyte membrane fuel cell system generates electrical energy through an electro-chemical reaction between the reformed gas supplied from the fuel reforming apparatus in the stack and the oxidant gas supplied from the oxidant gas supply unit.
The fuel reforming apparatus is constructed with a burner for generating thermal energy by direct combustion of a fuel, a reformer for practically generating a reformed gas in a reforming reaction between the fuel and steam using the thermal energy, and an evaporator for generating steam by receiving the thermal energy from the burner to evaporate water. Here, the steam refers to vaporized water.
In an existing fuel reforming apparatus, however, the burner, the reformer, and the evaporator are dispersively disposed, and therefore the thermal energy generated by the burner is transferred to the reformer and the evaporator. Accordingly, the burner does not directly exchange the thermal energy with the reformer and the evaporator, and therefore thermal efficiency is decreased.
In addition, in the existing fuel reforming apparatus, the burner, reformer, and the evaporator are customarily dispersed in their positions relative to one another, principally to accommodate operational conveniences, and accordingly the fuel cell system cannot be embodied in a compact size or arrangement.
Furthermore, the existing fuel reforming apparatus can achieve an optimal operational performance only when the thermal energy in the temperature range corresponding to the specific operational temperature is supplied to the reformer and the evaporator. It is difficult to control the thermal energy transferred from the burner to the reformer and the evaporator in order to maximize the thermal efficiency and the operational efficiency of the fuel reforming apparatus.